Thin, double-wall molded seat frame system

ABSTRACT

A seat frame for a vehicle or other seating comprises a seat back and a seat pan formed of molded double wall members having thin, substantially closed exterior walls and a substantially open interior. The exterior walls include front and back sections having a cavity therebetween, secured together to form a hollow, box beam type of structure. Integrally formed, spaced cup-shaped standoffs extend between the front and back sections between side walls thereof and provide internal reinforcement of the seat member between the side walls. The seat back includes a cavity for a seat back reinforcement member for either a restraint or non-restraint seat.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is based on and claims the benefit of the filing dateof co-pending U.S. Provisional Patent Application Ser. No. 61/237,926,entitled Thin, Double-Wall Molded Seat Frame System and filed on Oct. 4,2000, by Patrick M. Glance and Bradley M. Glance, the disclosure ofwhich is incorporated here by reference.

BACKGROUND OF THE INVENTION

The invention relates to vehicular seating generally and moreparticularly to a new vehicular seat frame.

Today automotive seat frames, for example, are constructed from a numberof materials and manufacturing technologies. Most seat frames and seatbacks are fabricated from steel tubing. Front bucket seat pans (a lowerseat frame utilized to mount a seat lower cushion) are commonly stampedsteel with a steel seat spring suspension, although a technologylimitation of steel seating frames is their large mass. Some seat framesutilize aluminum or magnesium, which has lighter mass, but is moreexpensive. Some seat pans are molded, glass-filled polypropylene orother molded resin systems.

Many automotive rear folding seats are blow molded, high-densitypolyethylene, or other resin. Some rear folding seat backs that doubleas a load floor in a down position, are compression molded, glass filledpolypropylene, blow molded high density polyethylene, blow moldedABS/polycarbonate, or other resin system. Some front seat backframe/trim covers are also molded glass filled polypropylene,polycarbonate, or other resin.

A technology limitation of molded seat frames is their relatively largemolding thickness, typically about 3 mm with ranges from about 6 toabout 2 mm. The large molding thickness results in a slow molding cycletime, and greater material usage, which directly results in a higherseat frame cost. A low resin tensile strength also contributes to largermolding thickness that is required to meet structural seat back loadrequirements. This is a technology limitation and natural consequence ofplastic seat frames.

These technology limitations have resulted in steel seat back framesweighing 6 to 8 pounds and costing $8 to $12, while steel bucket seatframe assemblies weigh between 4 to 6 pounds, and cost between $4 to $6.Aluminum fabrications are usually half the mass, but double the cost ofsteel. Magnesium frames usually cost more than aluminum.

Molded seat frames are typically expensive compared to steel frames, butare utilized for specialty, niche applications where the molded surfacedoubles as a styling show surface, a load floor, or is utilized toreduce mass in conjunction with metal reinforcement. Molded seat framesoften have a lower mass than their steel counterparts, at a higher cost.Lower mass is useful in improving vehicle fuel economy and may be afactor in the safety consideration.

Of course, the above comments assume that all the seat framealternatives are designed to the same or similar structuralrequirements. Regardless, a need for an alternative construction thatreduces mass at no cost penalty is clearly desired.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a molded seat frame thatlowers mass compared to conventional metal, but is cost competitive,comprises a thin, double-wall injection molded seat frame system.Theoretical studies indicate that a double wall injection molded,talc-filled high density polypropylene seat back, molded in a 1 mm wallthickness, will result in a 60% mass reduction, and a 25% cost reductionversus current technology steel frame systems. The key to this savingsis the use of the design principle of a closed box section with a thinwall structure that has continuous design stand-offs between the doublewalls to resist “thin wall buckling.”

The large area enclosed in a continuous jointed container is anextremely strong and efficient structure, especially during torsionalloading. The characteristic analogy in nature is an eggshell, but withadded integral, inter-connecting “stand-offs” to reinforce the thinouter shell, and improve structural strength.

A basic principle of this invention is the use of a thin wall enclosedstructure that is molded from two halves and jointed to create astructure with internal reinforcements either molded-in or “placed” inthe structure. This approach has advantages for improved productsimplification, reduced mass, improved structure, and incorporation ofdissimilar materials and reinforcement within the assembly.

For example, one design scenario is the use of an injection molding 1 mmthick, filled plastic in a half cavity shape. At the same time, acorresponding 1 mm half cavity shape may be molded and then the twojoined by hot plate welding, sonic welding, bonding, or other joiningtechnology. The injection molded two half design approach produces aproduct that is similar to a blow molded seat frame construction, butthe injection molding has further advantages of better componentthickness control, thinner wall, faster cycle time, and use of largervarieties of resins. It is possible to mold resins such as polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), thermosets, andglass-filled nylon, for example, which cannot be blow molded. The basicdesign concept also has application for metal die casting, such as zincand magnesium and vacuum injection molding.

Although the invention is described for automotive or over landvehicular seating, the basic invention has application for all vehicularseating applications including without limitation air, marine, bus, andrail. The invention may also be applied to office, home, and theatreseating, for example. The specific design sketches are for bucketseating, but the same principle applies for bench seating and couches.

These and other features, objects, and benefits of the invention will berecognized by one having ordinary skill in the art and by those whopractice the invention, from the specification, the claims, and thedrawing figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view of a double wall seat frame assembly,constructed in accordance with the present invention.

FIG. 2 is a perspective view as in FIG. 1 but also showing the internalconstruction of the assembly.

FIG. 3 is a fragmentary top plan view showing a left half of a seat panof a thin, double wall molded seat frame system of the invention, theright half being a mirror image thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right rear perspective view thereof;

FIG. 7 is an exploded right front perspective view thereof, showing topand bottom portions of an injection molded seat pan ready to be joinedat a common weld flange and at the base of various stand-offs;

FIG. 8 is a fragmentary left back perspective view of a left half of aseat back frame system of the invention, the right half being a mirrorimage thereof;

FIG. 9 is a fragmentary left front perspective view of the right half ofthe seat back frame of FIG. 8;

FIG. 10 is an exploded view of the view of FIG. 9, showing the front andrear portions of the seat back frame separated; and

FIG. 11 is a perspective view of a tower reinforcement member for anintegrated safety belt restraint system.

FIG. 12 is a perspective view of a tower reinforcement member for a seatthat does not have an integrated safety belt restraint system.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of a thin, double wall molded seat frame systemaccording to the invention is generally shown in the drawing figures anddiscussed below.

Referring to the drawings, FIG. 1 is a perspective view of a double wallseat frame assembly 10 constructed in accordance with the presentinvention. Seat frame assembly includes a seat back 12, a seat pan 14and a recliner mechanism 16 interconnecting the seat back and seatframe. The recliner mechanism is known.

A reinforcement tower 18 extends through an internal cavity 20 on oneside of the seat back. In FIG. 1, tower 18 is a restraint tower for aseat that incorporates an integral restraint system, wherein the safetybelt is attached directly to the seat back. A seat belt retractorhousing 22 is mounted on the top of tower 18. Where an integralrestraint system is not employed, a conventional reinforcement tower 24(FIG. 13) is employed instead of the longer restraint tower 18. Theshorter reinforcement tower can terminate at the upper end of recess 20.These components are known.

Seat pan 14 comprises a generally rectangular frame having a front framemember 26, a rear frame member 28, and side frame members 30, definingan open interior portion 32. A conventional resilient insert 34 can beinserted in opening 32. The insert may be formed of conventional insertmaterial, the insert being conventional.

Side frame member 30 and rear frame member 28 include reinforcement ribs36 in an upper surface thereof. The seat pan has recessed fastenerattachment areas 38 in the corners thereof for attaching the seat pan toa seat support structure in a vehicle. Front frame member 26 has anelevated contoured portion 40 that provides a desirable contour for legsupport at the front edge of the seat pan.

The construction of the seat pan 14 is shown in more detail in FIGS.3-7. As shown in FIG. 7, seat pan 14 is formed from a pair of molded,opposed cavity sections that are joined together to form a box beamhaving a generally open interior. The cavity sections comprise front orupper section 42 and a back or lower section 44. These are formedseparately and bonded together by hot plate welding, sonic welding,chemical bonding or other joining technology to form a hollow seat panconstruction.

Upper section 42 has an upper surface 46, outer sidewall 48, and innersidewall 50, with the rear side of the upper section being open. Lowersection 44 covers the open rear side of the upper section and hasflanges 45 and 47 at inner and outer peripheral edges that engage andare secured to the sidewalls of the upper section to form a closed boxbeam.

Independently spaced, conical, cup-shaped projections 52, preferablywith a circular cross section, extend downwardly from the upper surfaceof upper section 42 in the interior of the front and rear members 26 and28. These form standoffs that reinforce the interior portions of theseat pan. The standoffs in the upper section of the seat pan desirablyare opposed by corresponding standoffs 54 that extend upwardly from atleast the front portion of lower frame section 44. Lower standoffs 54can also be upwardly extending cup-shaped conical projections. The lowerprojections are shorter than the upper projections in the illustratedembodiment. The ends of the conical projections can abut each other, asshown in FIG. 6 and can be bonded together if desired when the seatframe is assembled. As shown in FIG. 6, the assembled seat pan comprisesa continuous peripheral sidewall, with a hollow interior reinforced byspaced standoffs. This reduces mass dramatically while retaining adesirable contour with desirable strength characteristics.

Desirably, the seat pan is formed by injection molding, although othermolding techniques will work. A satisfactory resin for the presentinvention is a talc-filled high density polyethylene (HDPE), but othermaterials are satisfactory.

The construction of seat back 12 is shown in FIGS. 8-12. For exemplarypurposes, the illustrated seat back is of a type that is capable of usefor an integral restraint mechanism. It should be understood that theseat back can also be a non-restraint type seat back. Seat back 12 isformed of the same double wall, welded, closed construction as the seatpan, with the seat back being formed in separate front and back sections56 and 58. The front section has a front surface 60 and sidewalls 62extending rearwardly to an open side 64. Back section 58 covers openside 64 and has a back surface 66 and flanges 68 that mate with thesidewalls of the front section. The sidewalls are welded or otherwisefastened to the flanges in a conventional manner to form a closed memberhaving a hollow interior.

Cup-shaped standoffs 90 are formed between the sidewalls at variouslocations in order to provide internal reinforcement for the seat backat positions between the sidewalls. In the illustrated embodiment, thestandoffs are generally rectangularly shaped, with opposing standoffsbeing formed on the inner sides of the back and front sections. Thestandoffs may abut each other and be fastened together when the opposedsections of the seat back are fastened together. It is contemplated thatthe standoffs could be in one section or the other but not both sectionsin appropriate cases.

The seat back of the present invention is formed in the shape of arectangular frame having side members 92, bottom member 94, and a topmember 96. Desirably, an integral head rest 98 is mounted on the top oftop member 96. The integral head rest includes side members 100 and atop member 102 extending between the tops of the side members. Anopening 104 is formed in the interior of the head rest. Similarly, anopening 106 is formed in the interior of the seat back 14. An insert 108formed of a plastic rattan material or other flexible material can coverthe opening 106. An attachment flange 110 can surround the interior edgeof opening 106 for attaching the rattan insert or the like. Theattachment flange can be formed of an elastic material such as aFlex-o-lator brand product.

One of the side members 92 of the seat back can have a hollow towerinsert cavity 20 therein for insertion of either a restraint tower 18 ora non-restraint tower 24. The restraint towers desirably are formed ofaluminum tube. A restraint tower is somewhat thicker than anon-restraint lower, with the restraint tower desirably being 2.2 mmthick and the aluminum material in the non-restraint tower being about 1mm thick.

With the seat back and seat pan formed in the foregoing manner, the seathas a desirable outer configuration and an inner configuration thatfacilitates mounting in the vehicle, and yet the structure islightweight, strong, and relatively inexpensive.

A particular bucket seat assembly is shown in the present invention. Itshould be understood that various other types of seat configurationscould be employed without departing from the spirit and scope of thepresent invention.

Among the advantages of the present invention, the seat is a hollow,internally reinforced, integrated structure created from two moldedcavities which are joined together to form a closed section containershape. This provides desirable strength, weight, and expensecharacteristics.

Another advantage of the present invention is that the seat frame panand seat back are formed in two cavity halves, which are molded togetherto form a closed box section. It is desired that the walls of the twocavities, in each case, are relatively thin (typically about 1 mm) andhence flexible, with internal, molded standoffs reinforcing the outerwalls when the two cavities are joined together. Notwithstanding theextremely thin walls, the seat frame pan and seat back provide goodstructural performance.

The seat frame pan and seat back can be formed from a number ofdifferent manufacturing processes, such as injection molding, twin sheetvacuum forming, vacuum die casting, casting, or compression molding. Theseat frame pan may be formed of a number of different materials, such ashigh density polyethylene, polypropylene, acrylonitrile butadienestyrene, polycarbonate, sheet molding compound, PBT, PET, or metal suchas magnesium, zinc alloy, or aluminum. Talc filled HDPE is typical. Theseat back can be made of comparable materials.

As shown in FIG. 10, the formation of the seat back in two sections alsofacilitates incorporation of the reinforcement structure formed ofmetal. In such a case, the reinforcement cavity 20 can be formed betweenthe front and back sections, with the reinforcement member in the formof tower 18 or 24 being positioned between the front and back sectionsbefore the back sections are welded or bonded together. The tower andother similar metal members for attachment or other purposes can thus beincorporated into the seat frame or seat back during the manufacturingprocess, thus facilitating attachment of the seat frame assembly to avehicle. It should be understood that the reinforcement tower or otherreinforcement member does not have to be inserted in the mold cavityprior to joining the two molded halves. Instead, the reinforcementmember could be inserted after the product has been formed and attachedby interference fit, adhesion, or mechanical fasteners. Even when thetower is inserted into the mold when the sections are attached together,such fasteners may be used to maintain the position of the tower in theseat back or the like.

It will be understood by one having ordinary skill in the art and bythose who practice the invention, that various modifications andimprovements may be made without departing from the spirit of thedisclosed concept. Various relational terms, including left, right,front, back, top, and bottom, for example, are used in the detaileddescription of the invention and in the claims only to convey relativepositioning of various elements of the claimed invention. The scope ofprotection afforded is to be determined by the claims and by the breadthof interpretation allowed by law.

1. In a seat frame comprising a seat back and a seat pan, theimprovement wherein at least one seat member of the group consisting ofthe seat pan and seat back comprises a molded double wall member havinga substantially closed exterior wall and a substantially open interior,with the exterior wall comprising opposed front and back sections havinga cavity therebetween, the front and back sections fitting together andbeing secured together to form a hollow, box beam type of structure. 2.A seat frame according to claim 1 wherein at least one of the front andback sections includes integrally formed, spaced cup-shaped standoffsextending between the front and back sections at positions between theside walls thereof, such that the standoffs provide internalreinforcement of the seat member between the side walls.
 3. A seat frameaccording to claim 2 wherein the standoffs include individually formed,conical, cup-shaped energy absorbing cells.
 4. A seat frame according toclaim 3 wherein aligned standoffs are formed in the back and frontsections, such that inner ends of aligned standoffs are adjacent eachother when the front and back sections are interconnected.
 5. A seatframe according to claim 1 wherein the at least one seat membercomprises the seat pan, the seat pan being formed in a generallyrectangular shape and having a hollow peripheral frame comprising afront member back member and side members, the frame having an openinterior, the front, back, and side members being box beam membersformed of the front and back sections, the front section being an uppersection and the back section being a lower section, the frame includinginterior standoffs extending vertically between the upper and lowersections.
 6. A seat frame according to claim 1 wherein the at least oneseat member includes the seat back.
 7. A seat frame according to claim 6wherein the seat back includes a hollow cavity for a seat backreinforcement member.
 8. A seat frame according to claim 7 wherein thecavity is formed along a vertical side of the seat back and is shaped toreceive a seat back reinforcement tower formed of a material dissimilarfrom the seat back.
 9. A seat frame according to claim 6 wherein theseat back comprises a generally rectangular frame having upper and lowerframe members and side frame members, with each frame member having abox beam configuration with a substantially hollow interior, the framehaving interior standoffs reinforcing front and back surfaces of theframe between frame side walls.
 10. A seat frame according to claim 9wherein the standoffs include spaced, cup-shaped energy absorbersmounted in at least one of the front and back members and extending in adirection between the members.
 11. A seat frame according to claim 1wherein a plurality of standoffs are formed on the interior of one ofthe front and back sections of the seat back, the other of the front andback sections of the seat back including standoffs that are aligned withthe standoffs in the one section, outer ends of the aligned standoffsbeing substantially abutting each other, the standoffs comprisingelongated, hollow projections.
 12. A seat frame according to claim 9wherein the frame has at least a partially open portion interior of theframe members, the frame members surrounding the open interior.
 13. Aseat frame according to claim 1 wherein the front section is contouredfor serving as a support for the body of a person seated in the seat,while the back section is provided with a different surface contour thatis designed to provide an acceptable configuration for attachment in avehicle, the different surface contours not requiring substantialadditional material in the seat member because of the hollow seat memberconstruction.